feat(ui): display media counts in library switcher

The UI had no surface showing how many media items have been imported.
Surface the total in the library switcher shown on the Dashboard, Series,
and Collections pages (via the LibrarySwitcher component) and in the
Bookshelf's inline library filter.

- Add a MediaCount field to LibraryData and a TotalMediaCount helper to
  sum counts for the "All Libraries" / "All Books" option.
- resolveLibrary() now fetches per-library counts (one query) and maps
  them onto each LibraryData entry, so the switcher reflects the active
  scope without changing the component's signature.
- Each library option renders "(N)" and the "All" option renders the
  grand total across the user's visible libraries.

The "All" total is the sum of the user's visible libraries, correctly
respecting per-user library visibility rather than a raw global count.

Regenerated templ files for library_switcher and bookshelf.

templates/library_switcher.templ

@@ -11,14 +11,14 @@ templ LibrarySwitcher(libData []LibraryData, currentLibraryID string, actions ..
 					class="px-4 py-2 rounded-lg border focus:ring-2 focus:ring-blue-500"
 					style="background-color: var(--bg-secondary); color: var(--text-primary);"
 				>
-					<option value="">All Libraries</option>
-					for _, lib := range libData {
-						if lib.ID == currentLibraryID {
-							<option value={ lib.ID } selected>{ lib.Name }</option>
-						} else {
-							<option value={ lib.ID }>{ lib.Name }</option>
-						}
+				<option value="">All Libraries ({ TotalMediaCount(libData) })</option>
+				for _, lib := range libData {
+					if lib.ID == currentLibraryID {
+						<option value={ lib.ID } selected>{ lib.Name } ({ lib.MediaCount })</option>
+					} else {
+						<option value={ lib.ID }>{ lib.Name } ({ lib.MediaCount })</option>
 					}
+				}
 				</select>
 			</div>
 			if len(actions) > 0 {